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Mike10956

How can I improve brakes on IB

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I use an 86 Carrera 2 for hill climbs fun rallies and track days. The brakes used to go away very quickly which I cured by using Castrol SRF to prevent boiling but they still vanish after a lot of hard use.I have been told that Boxster calipers should fit and with a bigger pad area should solve the problem any ideas.

Mike

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Welcome to IB- lots of opinions will no doubt follow.

All I'm going to chip in with is are you braking correctly? Lots of braking issues can be helped by braking for as short a time as possible. :twocents:

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Personally I've never experienced brakes on any of the performance cars I've owned as good as the AP 4-pot kit on the front of my 3.2.

 

They're great on the road, don't run stupid compound pads, yet I just cannot get them to fade at all on the track after even 30 minutes+ hard abuse. The other thing is they have so much feel you can totally ride near the lockup point without actually locking up. Granted, my car is a bit lighter than standard, but I seemed to be able to out-brake some quite expensive modern machinery at the recent RS day - although I have no idea how those cars were being driven.

 

Never had a car aside from this one where I didn't manage to get marginal on the brakes on track (maybe I need to check my technique!)

 

I inherited the kit from a previous owner, but in essence they are AP 5200-series calipers which can be widely bought, as can the floating discs, pads are DS2500 (or AP AF404's ;)). The calipers are laughably lightweight too compared to standard. I'd be happy to share part numbers and offer to have the adapter measured up, the company that supplied the kit is no longer trading so I don't think it would be stepping on anyone's toes to do so.

 

Rears are standard calipers and discs with DS2500.

 

No idea how they measure up to the Boxster brakes.

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A few observations.

 

1. What do you mean by "brakes going away" (where did they go to? on holiday?)? Seriously though, there are 2 potentials things you may mean. First is pad fade due to heat, where the pedal stays firmish but the pads are overheated. Second and much more likely, is the pedal lengthens due to boiling fluid due to heat. If you had a partial cure with SRF, lets assume its number 2.

 

2. How do bigger pads help with heat management? They don't.

 

3. Do bigger, aluminium boxster calipers help with heat management? Possibly, marginally. Anecdotally, people say they help, though in theory you should be able to generate more heat with them, so the problem may get worse. Maybe they transfer less heat to the fluid or cool better due to design.

 

4. The discs are your heat sink. The root of 3.2 brake issues are that the discs are too small, get too hot, calipers get too hot and fluid boils. One solution is bigger discs which usually come with a bigger/different caliper.

 

5. Step one. You have tried SRF and it helps because it has a higher boiling point. Next step is usually getting some air ducted in to the rotor centres. So, add 993 deflector plates to the A arms, remove backing plates, buy ducts, run hoses from fog light holes, add hub block off plates (otherwise the air spills through the hub rather than through the disc vanes). Also add race pads and sticky tyres so you stop more quickly. As Fraser suggests, the right technique is very hard short braking. You generate the same heat but maximise the cooling off period. No light braking. Ever. Rigorously enforced cool down laps. Pads replaced at 50% wear.

 

6. Step two. The above will work on a slightly LW 3.2 and provide all the brakes you need. BUT. You will still have a long pedal in the paddock from time to time and seals fry due to heat and its less than ideal. And it looks less cool than big flashy 4 pot brakes. So you bite the bullet and upgrade the hardwear. The brakes you want at this point revolve around a circa 300mm diameter front disc that is circa 28mm thick - so same as 964 front, early 944 Turbo front, Tuthills/Early 911/C12 kit presumably the AP Racing kit - that fits under 16 inch Fuchs. Anything that uses the standard small front disc is not really much of an upgrade.

 

You have options. When I did mine circa 10 years back you didn't. Easiest is the C12 kit that off the shelf gets you a bigger disc and 6 pot calipers and bolts on. Buy from Tuthills etc. Or, you reinvent the AP Racing kit. FWIW, I did the Porsche option and used 964 calipers (requires machining and adapters that I got from VCI in the US) over early 944T discs plus a 5mm bearing spacer. I also run the small C12 4 pot rear caliper over std rear discs (got sick of needing regular rear caliper rebuilds and small pads wearing out quickly). Like reddevil, this gives you "hand of god" type braking in a LW car (and access to sensibly priced parts thru dealers, indies etc as its all Porsche parts or pattern parts).

 

There are other ways of doing this, but I think I have covered the easiest ones. There is a thread on here using 996 brakes, for example, that would be very good, but IIRC, its not so easy.

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Actually at Donnington today in the wet I experienced a long pedal for the first time - not during the sessions but afterwards despite doing a slow cooling down lap. I think I could probably do with some of that cold air ducting to help cool off the brakes, obviously they had a lot of head soaked into them which seems to have done for the fluid.

 

Also I don't seem to be able to modulate the pedal as well as I could at Oulton, the recent geo has introduced some understeer and less crisp turn in, which seemed much more pronounced on the track than the road, so I guess I have a less planted front end and the fronts are more eager to lock.

 

CoG are having the car back in a few weeks to address.

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Fluid changed and brakes much improved - amazing what new fluid does for the feel even on the road!

Will also see if I can get some of the 993 deflector plates as Richard suggests.

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Will also see if I can get some of the 993 deflector plates as Richard suggests.

They were not expensive from the local OPC

DSCN3471.jpg

FOr maximum benefit it is worth making block-off plates to direct air through the vanes in the disks rather than letting it flow through the openings around the hub area.

DSCN3466.jpg

Mark

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Thanks for the info Mark, I'll check the back of my discs as it is a different setup to standard so may already have a plate installed.

The local OPC has robbed me of £36 for a pair of deflectors which I'll pick up and fit over the weekend.

Chris

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The local OPC has robbed me of £36 for a pair of deflectors

A of of inflation in 6 years, I paid about £6 each!

Mark

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And this apparently included the classic discount!

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I havent noticed much difference from standard pads moving to DS2500 for road use. Im sure in the track they will come into their own but I was hoping for some more initial bite.

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They are not very bitey until they have heat in them. Still not very bitey compared to a race pad with higher friction coef.

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Ensure your brakes are in good serviceable condition with quality fluid and suitable pads then spend your money on track driving tuition.

When used correctly you will be astonished how far the standard brakes on SC’s / 3.2’s will go before they reach the limit.

On the flip of this it is equally surprising how quickly a badly driven car will run out of brakes.

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Ensure your brakes are in good serviceable condition with quality fluid and suitable pads then spend your money on track driving tuition.

When used correctly you will be astonished how far the standard brakes on SC’s / 3.2’s will go before they reach the limit.

On the flip of this it is equally surprising how quickly a badly driven car will run out of brakes.

So True.....................

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Thanks for the info Mark, I'll check the back of my discs as it is a different setup to standard so may already have a plate installed.

The local OPC has robbed me of £36 for a pair of deflectors which I'll pick up and fit over the weekend.

Chris

I've had a go at fitting these, looking at the 993 front arms for reference. I can't get the deflectors any closer than about 50mm away from the bottom ball joint because the calipers will foul them on lock otherwise. Looking at the 993 the location of the front caliper is further up and further back (almost 45deg from the horizontal) rather than the vertical position on the IB cars. The location of the bolt holes on the 993 arms have the edge of the duct almost level with the ball joint, further outboard than I have them. I guess they pour air direct onto the disc

27748899631_66095e4a29.jpg

I'm not sure how effective they will be in the position I have them in, and I've only tie-wrapped them at present rather than p155ing around with modifying the a-arms if they proove to be in an ineffective position.

By the way had a measure up of the discs a week or so ago and they are a 313mm 28mm disc from memory.

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On the flip of this it is equally surprising how quickly a badly driven car will run out of brakes.

I think this is certainly true of my recent trip to Donnington in the wet. This is the first year in about 10 years that I have done a significant amount of track driving - and in the wet with a less than perfect handling car I was probably riding the brakes for a lot longer than I needed to. Still getting back into the swing of things.

As always the best money one can spend on a track car is tuition for the driver!

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...

There are other ways of doing this, but I think I have covered the easiest ones. There is a thread on here using 996 brakes, for example, that would be very good, but IIRC, its not so easy.

As Richard states, it requires some job to fit 996 Carrera brakes to an IB, but there are also a few upsides to it. The calipers are monoblock and therefore relatively light. The discs are not very large and therefore not particularly heavy. The brakes were also used on the power kit equipped 996 Carrera, so should even be able to cope with a somewhat tuned IB. Discs are surprisingly cheap, and they work with the stock hand brake.

But maybe most importantly, the consumables are standard Porsche parts and will most probably be available for a long time.

/Peter

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After a track day yesterday I found that the 3.2 brakes with ds2500 were no where near as confidence inspiring as the 964 track car I drove recently.

I like the idea of the AP racing kit or Boxster or 964 brakes.

Is there an option that required no machining?

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Is there an option that required no machining?

No machining for using Boxster calipers with 3.2 disks, but you do need adaptor blocks.

Mark

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No machining for using Boxster calipers with 3.2 disks, but you do need adaptor blocks.

Mark

Thanks Mark,

Do you know where I can buy this please?

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You could try proper pads to start with, either Performance Friction or Porterfield for example.

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The easiest upgrade is the Tuthills/Early911 kit with 300mm discs and 6 pot front calipers. Works with the std rears IIRC. Not the cheapest.

I don't think the little boxster caliper over 3.2 discs is a big upgrade but if heat is not the issue and pedal feel is the ask, then maybe that plus a 930 size master cylinder is what you want. 964 calipers over early 944T discs require adapters and machining.

While I used DS2500s in the 996TT and use them for road trips in the 3.2, I don't rate them very highly for feel. Even when hot, they don't really bite and pull you down from speed. To me, they feel more like a road pad and less like the entry level race pads, say Pagid Blue. They are a long way from something like a PF97 compound which is nowhere near state of the art. I would use PF everyday except for the dust that sets like concrete on the rims.

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